Vapor-phase processes are used for a variety of applications. For example, vapor-phase processes are used for chemical vapor deposition to deposit material onto a substrate, vapor-phase etching to remove material from a substrate or a reactor, and vapor-phase treatment processes to treat a surface of a substrate or a reactor.
Precursors or reactants for vapor-phase processes are generally selected according to a material to be deposited, etched, or treated; i.e., the precursors are generally selected to provide desired vapor-phase reactants. However, other factors are often used to select between more than one precursor that might be suitable for a particular application. For example, a reactivity or selectivity of a precursor may be a factor in the selection of the precursor. Another consideration for selecting a precursor is the stability of the precursor—e.g., does the precursor break down into other compounds before the precursor has a chance to take part in a desired reaction. Yet further considerations may include toxicity of a precursor, availability of the precursor, and cost of the precursor. Thus, a precursor that might have better properties, such as higher selectivity, reactivity, and/or provide more uniform deposition, etch, or treatment, may not be selected for a particular application, because the precursor is relatively expensive and/or toxic.
Remote or direct plasma systems may be used to create activated or energized species from a precursor, where the energized species are more reactive than the precursor for a given temperature. Remote plasma systems generally form a plasma upstream of a reaction chamber, and direct plasma systems generally form a plasma within a reaction chamber, where a substrate is often in or adjacent the plasma. Remote plasma systems may be advantageous over direct plasma systems for some applications, because the remote plasma systems do not form a plasma directly over a surface of a substrate. As a result, surface damage to a substrate that might otherwise occur in a direct plasma reactor can be reduced or eliminated using a remote plasma. However, remote plasma activated species from many precursors are relatively short lived and recombine or react with other components before the species enter the reaction chamber or reach a desired area of a substrate (e.g., a lower portion of a trench formed on a surface of the substrate and/or an outer perimeter of the substrate). Using a direct plasma allows the activated species to form within the reaction chamber, but the activated species may still recombine or otherwise become inactivated prior to reacting desired areas on a substrate.
Accordingly, improved methods and systems for forming desired, relatively stable intermediate reactive species, using a remote plasma system are desired.